Interface superconductivity in La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_{4}$/La$_{1.84}$Sr$_{0.16}$CuO$_{4}$ bilayers

TL;DR

This study demonstrates the existence of a distinct two-dimensional superconducting phase at the interface of La-based cuprate bilayers, characterized by a Kosterlitz-Thouless transition and sensitive to magnetic fields.

Contribution

It provides experimental evidence and a theoretical model for interface superconductivity in cuprate bilayers, highlighting inter-diffusion effects and 2D behavior.

Findings

Interfacial layer thickness ~25 nm

Superconductivity governed by Kosterlitz-Thouless transition

Magnetic field suppresses Tc with H^2 dependence

Abstract

We identify a distinct superconducting phase at the interface of a La$_{1.48}$Nd$_{0.4}$Sr$_{0.12}$CuO$_4$ (LNSCO)/La$_{1.84}$Sr$_{0.16}$CuO$_4$ (LSCO) epitaxial bilayer system using ac screening measurements. A model based on inter-diffusion of quasiparticles and condensate at the interface yields a thickness of $\sim$ 25 nm for the interfacial layer. Two-dimensional superconductivity of the interface layer appears to be governed by Kosterlitz-Thouless-Berezinskii transition. A parallel magnetic field suppresses the superconducting transition temperature of this layer with a pair breaking parameter $\alpha$ varying as $H^2$.